Sen. Amy Klobuchar (D-Minn.) speaks during the Women’s Convention in Detroit on Oct. 27, 2017. (Anthony Lanzilote/Bloomberg)
Opinion writer

Welcome to the start of the 2020 presidential race. If Democrats look at their impressive wins in governors’ races (despite losing in Ohio), suburban wins in the House and a huge gender-gap advantage coupled with some big disappointments for high-profile progressives, the arguments for candidates in the mold of Sen. Bernie Sanders (I-Vt.) or Elizabeth Warren (D-Mass.) look weaker Wednesday morning. (House candidates whom Sanders campaigned for batted only .500, with five wins and five losses.)

When you look to the Rust Belt and Upper Midwest, moderate Democrats such as Sen. Amy Klobuchar (D-Minn.) and former vice president Joe Biden look like they could duplicate wins in gubernatorial and Senate races in Michigan, Wisconsin and Pennsylvania. Watching the close-but-no-win races in Florida’s governor’s and Texas’s Senate races, Democratic primary voters may be nervous about nominating a fast-rising liberal such as Sen. Cory Booker (D-N.J.); former Massachusetts governor Deval Patrick’s more moderate image may convince Democrats that he’s the safer pick. The biggest takeaway for Democratic primary voters for 2020 should be: Not just any candidate is going to win, certainly not a progressive star who can be painted as a far lefty and will struggle in purple states. The question should be: Who is going to keep all those suburban voters in the Democratic fold?

On the GOP side, there was bad news for those hoping for an improbable primary victory over President Trump. The GOP is becoming redder, more rural and more akin to a Trump cult by the minute. You very well may see the stampede of women, moderates, suburbanites and college-educated voters out of the party. Does a reform-minded moderate such as Ohio Gov. John Kasich have a chance in this GOP? It’s hard to see how. And, given the number of new red-state Republicans in the Senate whom Trump helped win, it’s hard to see any real opposition building from the right, either.

Now it’s possible a devastating report from special counsel Robert S. Mueller III or an economic downturn — if the economy weren’t so strong, can you imagine how many more House seat would have been lost? — would weaken Trump’s grip on the party. But after Tuesday, the GOP looks more Trumpian than ever.

And that does raise the prospect of a third-party or independent candidate running in the center-right lane. The prospects for such a candidate depend largely on what Democrats do. The great middle of the electorate from center-right to center-left is looking for a political home. They’re certain at this point that the GOP in the grip of Trump is not for them. If Democrats do run a Midwest or Rust Belt moderate — or a competent governor or ex-governor from the coasts (e.g., Patrick or Washington state Gov. Jay Inslee) — they may be rewarded with a broad-based coalition that provides an electoral college win (comprised of the coasts, the Upper Midwest and the Southwest).

If, however, Democrats over-interpret the House victories and ignore the kind of Democrats who won in the suburbs and in numerous governors’ races, they might be tempted to go with a candidate who chases those suburban, college-educated and white women voters away — giving an opening to a Kasich or other middle-of-the-road Republicans or ex-Republicans to seize the vast middle.

If nothing else, midterms remind us how diverse the country is and the limits of turn-out-the-base elections when you need to operate outside deep-red and deep-blue locales. A presidential candidate will need to scoop up all the diverse segments of the electorate whom Trump has made perfectly clear have no home in the GOP.

Read more:

Megan McArdle: Both Democrats and Republicans are losing this culture war

Max Boot: The battle with Trumpism is just beginning

Tom Toles: And now Democrats need to play the long game: Helping younger Americans

Jennifer Rubin: Republicans pay the price for racism and xenophobia

Greg Sargent: Three of Trump’s biggest fables died last night

Jennifer Rubin: Democrats take House as voters give Trump a big thumbs down